Process for testing oils



March 20, 1962 G. R. SCHULTZE ET AL 3,025,698

PROCESS FOR TESTING OILS Filed Oct. 28, 1959 PRESSURE IN CM. WATER I i I POOR MIDDLE RANGE FOR HD OIL HD EFFECT INVENTOR.

GEORGE R. SCHULTZE JOHANN EG.FUHRMANN 3,Z5,698 Patented Mar. 29, 1952 3,025,698 PROCESS FOR TESTlNG OILS George R. Schultze, Gcrlachstr. 24, Hannover, Germany, and Johann F. G. Fuhrmann, Friedrich Eggersstr. 30, Wedel, Holstein, Germany Filed Oct. 28, 1959, Ser. No. 5,582 6 Claims. (Cl. 73-53) This invention relates to a novel process for determining the detergent-dispersant properties of heavy duty lubricating oils and the like.

The increasing demands technology has made on oils for the most varied purposes, especially on lubricating oils, have led to an even greater use of so-called blended oils, the properties of which are adapted to the particular purpose for which they are to be used by means of certain additives. These additives serve the purpose, among others, of improving the viscosity character, depressing the pour point, raising the resistance to oxidation and rust, preventing foam formation and keeping the lubricating surfaces free of deposits, as well as of dispersing mud, coke and particles of carbon black. The motor lubricating oils blended with additives for the above purposes have become known as HD (heavy duty) motor oils.

Attempts have been made by means of various methods, for instance, by chemical examination, by measurement of absorptive properties or by photometric evaluation of the sedimentation behavior of specially prepared suspensions of carbon black in the oil to be tested, to determine, botht qualitatively and quantitatively, the properties of HD oils containing various additives. However, it has been found that definitive evaluation of a motor lubricating oil has hitherto always required testing in a motor under operating conditions as closely similar as possible to those prevailing in practice. The procedures developed for such testing of oils in motors are, however, exceedingly costly and time-consuming. They require running periods of between 50 and 480 hours and are therefore unsuitable as a means of providing a simple and prompt answer to the question of whether or not an oil belongs to the category of HD oils, or of clarifying whether or not certain subtances will be suitable as additives. It is particularly in connection with the development of additives, but also for purposes of production control in the manufacture of motor oils, that there has long been the need of a rapid and simple test to determine content of surfaceactive agents and in particular of additives with detergent and dispersant effect. This purpose is fulfilled by the process of the present invention.

It is accordingly the principal object of this invention to provide a novel process for determining the detergentdispersant properties of heavy duty lubricating oils.

It is another object to provide such a process which is simple, expeditious and easy to perform and by which the dispersant and detergent additive content of the oil may quantitatively be ascertained.

This invention is based on the remarkable finding that the thickening of an oil with certain finely divided substances which, depending on the amount added, form a paste or solid plastic mass, can be more or less extensively reversed by the presence of surface-active substances, such as the detergents-dispersants, so that the pastes will either soften or even liquify completely. As will be shown in detail below, the change in consistency of an oil thickened by means of finely divided substances is a measure of the presence and amounts of additives in a given oil to be investigated. For the practical application of the process according to the invention, the procedure is to prepare a test paste from a pure rafinate, i.e. one containing no blended additives of any kind, thickened by means of such a finely divided substance, then to add this test paste to the oil to be tested, and to determine the change in consistency, for example, by viscosity measurement, of the test mixture thus obtained.

As already mentioned, a raffinate of maximum purity, preferably a white oil, largely free of polar constituents, is used for the preparation of the test paste. This white oil is thickened by stirring with a finely divided metal oxide, this term for the purpose of this invention including metalloid oxides, obtained pyrogenically, preferably in the form of an aerosol, by oxidation or hydrolysis at elevated temperature of the volatile metal or metalloid compounds in the gaseous phase and separated in the form of an aerosol. Such oxides referred to generally as pyrogenic oxides since they are produced at flame temperatures, are obtained with extremely active surface and small primary particle size, e.g. of between 5 and 25 cm. l() in the case of silicon dioxide. Among these oxides, aluminum oxide and, especially, silicon dioxide have proved to be particularly useful with reference to the sharpness of the consistency change as a function of the HD grade of the oil to be tested.

While stirring of the ingredients may be sufficient in order to prepare the paste, it was found that using a double or triple roller mill is preferential to mere stirring for preparing the paste. It is also possible to stir, to work or to roll together, all at once in appropriate concentrations, the white oil plus the finely divided metal oxide plus the oil to be tested for its detergent-dispersant properties.

The starting material of the test pastes should be present in suflicient quantity that the paste will not change its consistency to any appreciable extent upon addition of an oil containing no additive in an amount at least as great as would be required for the performance of the test on HD oil. The test paste must, therefore, be so constituted, for example, that upon addition of a like amount of a white oil it would still retain its consistency as a plastically solid mass. This is generally achieved by dispersing approximately 10% of the oxide into the unblended oil. After manually or mechanically working in the oxide, the mixture is then passed through a three-roll mill a number of times and thus given its final consistency. The paste so obtained is a gel fat of approximately 7000 mm. H O (Kesternich consistency).

When this paste is combined with an unblended base oil in a proportion of 1:1 and stirred or mechanically worked for approximately 5 minutes, the mixture will likewise remain plastically solid and exhibit practically the same consistency as the test paste. If, however, an HD oil instead of a base oil is added, a highly fluid mixture is obtained, the flow characteristics of which differ distinctly from those of the solid test paste.

Although the oil to be tested and the test paste are generally mixed in a proportion of 1:1, it may also be necessary in the case of especially highly blended oils to use 2 to 4 parts of test paste per 1 part of oil to be tested if, in addition to the qualitative determination had an HD oil is present, one also seeks quantitative data on the degree of blending of the oil investigated. One can, of course, also mix the oil to be tested with the paste in the proportion of 1 part oil to less than 1 part test paste if the properties of the oil to be tested should make this necessary for a measurable determination of the change in consistency.

It has already been mentioned that the process according to the invention furnishes not only a qualitative result with regard to the presence of HD additives, but, as the examples below will show, also makes it possible to obtain quantitative information on the nature and properties of the oil tested. Particularly noteworthy in this connection is the fact that the test process of this invention is also sensitive to a reduction of the HD properties caused, for example, by the addition of methacrylate viscosity ameliorants. It is known and demonstrable in motor tests that the HD quality of an oil is affected by the concomi- 8,0 3 tant use of such viscosity index ameliorants, especially methacrylates, and that the desired cleaning and finely dividing effect must be compensated by a greater addition of detergent-dispersant additives. The test process according to the present invention also reproduces this state of affairs, in that testing of HD oils containing methacrylate additives which improve the viscosity index reveals only a slight change in consistency or decrease in viscosity when the test paste is added. During the testing according to the process of the invention, the oil containing methacrylate additives, in conformity with the results of the motor running test, behaves as if it contained no or only slight amounts of HD additives. If, however, an amount of detergent-dispersant additive or additives is added which is suificient to compensate the reduction of the detergent-dispersant properties caused by methacrylate, the test process will indicate this compensation fully correlative with the test procedure in a motor under operating conditions.

The following examples are representative of the process of the invention.

EXAMPLE 1 Various oil mixtures, hereinafter designated by A, B, C and D, were tested both by the process according to the invention and by the engine test with a view to determining their properties. The oils used in each instance consisted of the base oil with specific detergent-dispersant additives present in amounts ranging from 0.4 to 1.2 percent by weight. In addition, oils C and D contained respectively 2.5 and 1.3 percent by weight of a methacrylate ester viscosity index ameliorant. Control tests on the same oils were run in a MWM KD 12E diesel engine under full load for 75 hours at a speed of 1850 rpm. The diesel fuel used was one which had been cut with special gas oil to a sulfur content of 1 percent by weight and which had a cetane number of 45. The results of the motor test, confined to piston rating made on a point basis, the disaces short outflow time of which in the test process according to the present invention proves this to be the case. The extent of the consistency change is thus fully correlative with the results of the motor test run. The same is true of oil B, the 90-point rating of which still places it within the range of good HD oils, but the HD properties of which exhibit a somewhat lower effectiveness. This fact is of course also reflected in the test process, as evidenced by a somewhat greater outflow time.

After the test run, which in the case of D had to be interrupted after 26 hours, oils C and D exhibited extensive fouling of the piston, with deposit of a solid varnish-like layer on the first ring groove and on the piston head. As regards their HD properties, both oils proved to be failures in the motor test, oil D having been found to be considerably worse than oil C. Here, too, these relationships are clearly borne out by the testing process according to the invention, in agreement with the results of the motor test.

EXAMPLE 2 Other blended oils were subjected to a comparative test procedure similar to the one used in the case of Example 1. These oils are designated by the letters E, F, G, H, J and K. Oils F, G and K are mixed with 2%, 3% and 4% of the same detergent additive. Oil H was blended in the same manner as oil E, but in addition contained dithiophosphate as anti-oxidation additive. Oil J, just as oil H, contained a dithiophosphate additive, but a detergent-dispersant additive of a different kind. A different kind of detergent-dispersant additive was also added to oil K. Table 2 shows the results of the test in accordance with the process of the invention, the magnitude of measurement being again given as the outflow time at a given pressure. The oils in the second line are entered with quality indices which run from 1 to 5 to reflect increasing HD properties. The third line of the table shows the over-all HD grade rating, as obtained in the motor test.

Table 2 Oils Designation t E F G H .T K

Test process acc. to invention:

Outflow time/pressure (cm. water) /20. 95/20 64/20 l4/20 l9/20 19/20. Sequence reflecting increasing H D properties... 3 l 2 r 4 4. Motor grading good not tested... 4 pts. inlgrior good good... not tested.

to Oil persing efiect determined by means of a spot test and microfilms, and the general HD properties are listed in the table below for the four oils. The same table also contains, in the last line, the results of the test carried out in accordance with the process of the invention. The magnitude of measurement used is the outflow time of the test mixture after admixture of the particular oil being tested with the test paste prepared with silicon dioxide as described above.

This table also shows that the test process according to the invention, with the aid of the determination of the consistency change, is qualitatively in agreement with the results of the motor test.

EXAMPLE 3 It has already been stated that, by changing the proportion of test paste to oil, quantitative data can be obtained on the degree of blending. To that end, oils with T able 1 Oils Designation A B C D Piston rating (points).. 994 44 -11. Dispel-sing etiect excellent fa1r pooix .T-ID properties (1 none none.

0 good 'lest acc. to the inven- 26 see/1G0 mm. H 0 001- sec/100 mm. H2O

column (good thintion (outflow time). umn (marked thinning out).

ning out).

no flow at 100 min. H O column (no thinning 1 Evaluation after the test was stopped in the 26th hour of the test run because at this point the oil was no longer capable of full lubricating effectiveness.

The above table shows that oil A is a motor oil with varying degrees of blending were tested with regard to the remarkable HD properties, the marked thinning out and 75 addition ,of detergents-dispersants by the process accordwith small paste admixtures.

ing to the application. The results of these tests are illustrated in the accompanying drawing in the form of curves which reflect the dependence of the outflow time of the test mixture on the pressure. The completely solid line curves designated with the letters J, K, L, M, N, O, P and R reflect the outflow values in cases where both oil and test paste were mixed in a proportion of 1:1. The broken-line curves L, O, P, Q and R represent the results of the test with a proportion of oil to test paste of 1: 1.5 in the case of L, O and Q and a proportion of 1:2 in the case of P and R. The solid-line curves in the figure indicate that oils I and M exhibit poor detergentdispersant properties (cf. also the classification Range of HD Oils in the margin of the figure). All the other oils possess good to average detergent-dispersant properties. When the proportion of test paste in the test mixture is increased, as reflected in the broken-line curves, oils L and (now being designated by L and 0') apparently drop to the range of average HD grades, whereas oils P, Q and R do not undergo any change in classification as good HD oils even under these test conditions. Obviously, this deviation is due to the fact that oils L and O are comparatively lightly blended oils, whereas oils P, Q and R contain substantially higher amounts of additive. Consequently, even with large proportions of finely divided oxide contained in the test paste, the oilbinding power of the oxides is terminated because of saturation thereof by the additives. There is consequently a thinning out of the test mixture, as is also the case The lightly blended oils, however, because of their low content of detergent-disperant additives, are not able to eliminate the thickening effect of all the oxide contained in the test paste, and consequently exhibit but little change in consistency. At

high paste concentrations, they maintain a high consistency and apparently behave like a base oil without HD additive.

This example shows that, by carrying out the process according to the invention with two or even three difierent paste concentrations in the test mixture, the amount of HD additive can be determined.

Having thus described our invention, We claim:

1. Process for testing oils for their content of surfaceactive agents, particularly heavy duty motor oils for their detergent-dispersant effect, characterized in that oil to be tested is mixed with a test paste consisting of a pure raffinate and a finely dispersed pyrogenic metal oxide, and measuring the change in consistency of the test mixture so obtained.

2. Process in accordance with claim 1 in which the metal oxide is selected from the group consisting of aluminumoxide and silicon dioxide having a primary particle size of less than cm. 10".

3. Process in accordance with claim 1, characterized in that the consistency of the test paste is so adjusted that it still remains plastically solid when admixed with an amount of rafiinate corresponding to the amount of oil to be tested.

4. Process in accordance with claim 1, characterized in that said test paste contains about 10% of the finely dispersed metal oxide.

5. Process in accordance with claim 1 characterized in that the rafinate is largely free of polar constituents.

6. Process in accordance with claim 1, characterized in that the oil to be tested and the test paste are mixed together in proportions of between about 1:1 and about 1:4.

References Cited in the file of this patent UNITED STATES PATENTS 2,841,980 Kay July 8, 1958 

1. PROCESS FOR TESTING OIL FOR THEIR CONTENT OF SURFACEACTIVE AGENTS, PARTICULARLY HEAVY DUTY MOTOR OILS FOR THEIR DETERGENT-DISPERSANT EFFECT, CHARACTERIZED IN THAT OIL TO BE TESTED IS MIXED WITH A TEST PASTE CONSISTING OF A PURE RAFFINATE AND A FINELY DISPERSED PYROGENIC METAL OXIDE, AND MEASURING THE CHANGE IN CONSISTENCY OF THE TEST MIXTURE SO OBTAINED. 